Welcome to my Home Draught Dispensing Page!
part of Jeff Stanley's draught site CLICK HERE
This page is best understood by
reading it from start to finish. If you are in a hurry and
are looking for specific information you may follow these links
within the page.
Understanding pressure in dispense
Understanding the temperature / pressure balance
Understanding pouring problems
Quality Issues (cleaning, shelf life, glassware)
Selecting the right type of tubing
Using the proper restriction (line length)
The first thing you need to understand is carbonation. CO2 is a gas that dissolves easily into water (and beer). The amount of gas dissolved into beer is measured in volumes. If one liter of beer is carbonated to 2.5 volumes, then there are 2.5 liters of CO2 gas dissolved into the beer.
CO2 gas has little or no detectable flavor, but as gas comes out of the solution (bubbles and foam), it does release aromas and flavor characteristics in the beer, affecting the flavor. When a brewer produces a beer, he takes care to control the carbonation level in a way to bring out the flavors and aroma, to effect the flavor in a controlled way. Usually, beers with a strong bitterness and aroma are not carbonated as highly as beers with less flavor and aroma.
For example, Bass Ale is carbonated to 2.2 volumes of CO2. Bass has a fruity sweet flavor and a decent amount of bitterness and aroma from hops. A relatively low CO2 level of 2.2 volumes compliments it perfectly. It makes the beer feel smooth in the mouth and releases just the right amount of the complex hop and malt aroma.
On the other hand, Coors Light has 2.8 volumes of dissolved CO2 (from Golden, CO brewery). Coors light is not very malty or "hoppy", therefore it has more CO2 to help bring out the "qualities" it does have.
Pressure, measured in pounds per square inch, is defined as the force at which the CO2 molecules in the head space of the keg push on the beer. As the pressure increases, the gas hits the beer with more force and dissolves into the beer more easily. As the pressure decreases, the gas does not dissolve into the beer as easily and gas can come out of the beer.
High pressure increases the carbonation level, low pressure reduces the carbonation level. The right amount of pressure in a keg will maintain the right carbonation level.
Most breweries or distributors can give you suggested pressure settings for the beers they sell. If you make your own beer use a carbonation chart to determine the proper pressure.
The temperature of the beer effects the amount of pressure needed in the keg to control the carbonation level. As temperature increases, CO2 bubbles expand and will come out of the beer. As temperature drops, CO2 dissolves more easily into the beer.
For example, at 38 degrees F, Coors Light needs 15 psi to maintain its CO2 level. At 40 deg F it needs 16 psi. At 36 deg F it needs 14 psi.
Generally, a two
degree increase in temperature requires a one pound increase in
pressure. A two degree decrease in temperature requires a one
pound decrease in pressure.
Illustration "A"
represents CO2 pressure adjusted properly for the storage
temperature and carbonation level of the beer. There is an
equal amount of CO2 dissolving into and breaking out of the beer.
Illustration "B" represents too little CO2 pressure. Gas breaks out of the beer into the head space of the keg and in the lines. Pockets of gas will accumulate in the lines creating pouring problems as well as flat tasting beer.
Illustration "C" represents too much CO2 pressure, more CO2 is dissolving into the beer than is breaking out. The carbonation level of the beer is increasing. Pouring problems and "buzzy" tasting beer will result when the keg is low and dispenses the over carbonated beer. Over carbonated is often perceived as tasting extra bitter.
Pouring problems result when beer goes flat while in the lines or a keg is exposed to too much pressure for too long. These problems can be cured by having enough secondary regulators to run each beer at it's ideal gauge pressure and being careful to store the beer at an even temperature.
Low Pressure
If your beer is going flat while in the lines it is caused by the pressure being set too low. It will be obvious to you because the beer line will collect pockets of CO2 gas.
These pockets of
gas will be worse the longer you go between uses of the
tap. They will also be worse when the keg has a lot of beer
in it because as the gas breaks out of the beer, it will
eventually become flat enough that the problem will stop.
You will usually experience this problem during at least first
half of the keg.
The pockets of gas collect
right above the keg and directly behind the faucet; therefore
when you open the faucet you will get a shot of foam, about 4
ounces of clear beer, followed by another shot of foam; after
which the beer will pour clear until the tap is at rest for 10
minutes or so, allowing the gas pockets to build up again.
Remember that as the temperature of the beer increases, it will
require more pressure so these same symptoms will occur if the
cooler or beer is more than 4 degrees higher than what the
pressure was set for. This is why it is important to keep
the beer at a constant temperature. Whether you are using a
keg box, refrigerator, or a walk in cooler it is important to
keep the door closed so that the keg temperature does not
fluctuate. If you are using a keg box it is not wise
to store garnishes, tomato juice, or liquor bottles in the cooler
that would require you to open the door frequently. Gas
will also break out of the beer behind the faucet if the dispense
tower is not cooled properly. There should be some sort of
way set up to force cool air into the tower. If the tower
is not cooled properly it can also cause the section of line in
the tower to build up a lot of yeast growth. No matter how
often you have your beer lines cleaned this build up, due to warm
lines, will cause problems with off taste product.
High Pressure
If your keg is exposed to too much pressure or is on line for too long you will experience problems caused by over carbonation. Over carbonation symptoms appear when the carbonation level of the beer increases because the pressure is set too high.
Mild over carbonation symptoms
usually closely resemble those caused by beer going flat in the
lines. The difference is that they will appear when the keg
is nearly empty (the last 1/3 or so). Remember that as the
temperature of the beer drops, it needs less pressure to maintain
the proper carbonation level. Because of this, you may see
these problems if your beer is stored on line at temperatures
less than 35 degrees F. The ideal temperature range for keg
storage is 35 to 40 degrees F.
( I receive a lot of email about this
claiming 40 degrees is too cold. I recommend you never
allow your draft beer to get warmer than 43 degrees F at any
point in the system because the beer is more protected from
spoilage and oxidation. If you like your beer warmer than
this, rinse your glass with warm water before pouring and keep
the keg stored at 35 - 40 degrees.)
Beer in direct contact with the gas picks up the CO2 first. It takes a lot of time for the gas to absorb deeply into the beer so over carbonation usually is most evident at the end of the keg. If you tap a fresh keg and it is very foamy, there is a 99.9% chance that the problem is not over carbonation.
Five things must be done to maintain the quality of the beer being dispensed.
The first is to prevent oxygen from entering the keg. If your keg is going to last more than two days you must use CO2 to pressurize the keg. Hand pumps are not OK for anything other than one night long parties. 'Nuf said.
Second, the beer must be consumed in a reasonable amount of time. Draft beer is generally only good for 45 days after it is filled. Don't buy a keg to save money if you cannot consume it in a reasonable amount of time, you will be doing yourself a favor to only buy as much beer as you can consume in a week, two at the most. 1/4 bbls and 1/6 bbls can be a good solution to this.
Third, the beer must be kept cold. The 45 day expiration date usually assumes the beer will be kept below 40 deg F. Higher temperatures greatly accelerate spoilage. The entire system must be kept cold, from the keg to the faucet. A good rule is to treat beer the same way you would treat milk.
Fourth, the system should be cleaned after every keg or every two weeks, which ever is longer. Line cleaning kits for home systems are available and usually cost under $50 - $80.
Fifth, you must keep the glassware in very good condition. If you do not use cleaner designed for bar glasses then beer glasses should be cleaned especially well and rinsed very well. Always allow them to air dry, do not towel dry. If (god forbid) you freeze your glasses, don't put them in the freezer 'til they're dry. Freezing your glassware will destroy the beer's flavor and cause a lot of foam.
Most people cannot follow these steps properly, someone invented cans and bottles for this reason.
There are many brands of pressure regulators. The prices vary greatly, all are basically the same. There are a few features that are important to look for.
There should be secondary a pressure gauge that reads, at most, 60 psi. Gauges that read higher than this are difficult to adjust accurately.
Many regulators also have a high pressure gauge to read the amount of gas in the bottle. The high pressure gauge should be used in systems that do not have a back up bottle of CO2 so there will be enough warning to get a new bottle. Always replace the bottle once the pressure on the secondary gauge begins to drop and nears the red area of the high pressure gauge. When the primary pressure gets low in the bottle the secondary pressure will begin to drop. You will not lose very much CO2 if the bottle is changed before it is empty, and you will prevent pouring problems that waste beer.
What brand to use? Any vinyl line that is brewery approved sold by a draught parts distributor is usually ok, but there are things to look for. Always get clear line for gas and beer. This will allow you to see if the line is clean and aids troubleshooting (I will cover this later). It is possible for the thomas (check, one way) valve in the tap to fail and let beer into the gas line, clear line will let you see this and fix it. Of course, clear beer line lets you see yeast and beer stone build up in the line plus it will let you actually see the gas breaking out of the beer when the pressure is set too low. Air line is usually 5/16" id and beer line is always 3/16" id (in a short system). Using 1/4" id or larger for beer line will not restrict your system properly and prevent the proper pressure adjustment. Ask for the restriction value (pressure drop) of the line when you purchase it.
There are three basic types of
beer faucets. First, the regular ordinary faucet you will
see in every bar on the planet; second, the little plastic one
that hooks directly to the line; and third the euro type that is
most common in dispensing Guinness.
Unless you plan on serving Guinness
on tap in your home, the ordinary faucet is the best choice.
Never use the little plastic faucets
for co2 dispense, they only work well on hand pumps, under low
pressure, for one day parties.
If you occasionally serve Guinness
or a similar product on tap at home, the euro style faucet will
work on all beers if you remove the little disc from the plastic
output spout. The disc has 5 tiny holes in it and serves to
strip out what little co2 Guinness has, giving it the special
head characteristics. Any beer carbonated over about 2.0
volumes will be all foam if poured through the disc. When
dispensing a low co2 level Guinness type beer through the disc it
takes a lot of extra pressure, usually 20 to 30 psi. Using
pure co2 will ruin the beer at this pressure. If you
dispense using the euro faucet with the disc, most breweries
suggest 25% co2 / 75% nitrogen "beer gas" at 30 psi.
Faucets must be cleaned at least
every two weeks. The faucet spout is exposed to air and
will pick up a lot of wild yeast growth, it has to be cleaned
regularly! If you have a home keg setup you must
invest in a cleaning kit that comes with a faucet wrench and a
faucet brush.
The shank is the threaded metal pipe that attaches to the beer line at one end and the faucet at the other. There are two things to consider when buying a shank. First is the length. If you are using an old fridge, the shank needs to extend into the fridge about 6" to help keep it and the faucet cold. The other thing to consider is the inside diameter. Always use a 1/4" id shank. This reduces the force the beer hits the back of the faucet with and reduces foam. Some more highly carbonated beers will not pour through a 3/16 shank without a LOT of foam. All beers pour better through a 1/4" shank. 'Nuf said.
The system restriction controls the flow rate of the beer from the faucet. Most of the restriction comes from the beer line. There is also restriction from gravity and from some draught equipment but it has little effect (less than 1 foot of length) on most short systems. (If your system has a lot of vertical rise or fall, gravity has .5 lb/ft of restriction) Using equal pressure and restriction gives a flow rate of 1 gal/min. This is usually too fast. The best way to determine the right length is to take the ideal pressure, add 5, divide by the line's restriction value per foot. If the beer pours too slow for you, shorten the line 6" at a time.
Example:
System is 38 degrees.
Distributor recommends 12 psi at 38
deg for the beer you are serving.
Parts vendor says the line has 3
lb/ft of restriction.
12 psi plus 5 (to slow) = 17
17 divided by 3 (line restriction
value) = 5 ft 8 in of line
System needs 5 ft 8 in of line at 12
psi
YES, IT IS THAT SIMPLE
